179 at a lower temperature; and hence probably it, is, that liquid oxy muriate of lime burns the phosphuretted hydrogen, not the hydrogen gas. The quantity of oxygen necessai'y to saturate a given volume of phosphuretted hydrogen is easily found. Oxygen gas containing a known per centage of azotic gas, must be used in some excess, mixed with a doe portion of the gas. After exploding the mixture, the loss must be observed, and then the remaining oxygen most be found by exploding it with hydrogen. Hence the trne volume of oxygen spent by the first explosion, and that of the combustible gas are both determined. The due proportion of oxygen is so nearly 2 to 1, that I have not been able to determine on which side the troth lies. Dr. Thomson says that when phosphuretted hydrogen and oxygen are mixed, two volumes to one, a white smoke takes place9 the volume of oxygen gradually disappears, and there remains behind a quantity of hydrogen exactly equal to the original volume of the phosphuretted hydrogen. I have observed nothing at all like this- A mixture of phosphuretted hydrogen and oxygen stood 24 hours without sensible diminution9 and afterwards being* exploded, 0 vrhlrtfVkjao f\r f^-w •K7